We were sold out of a book that her kid needed for homework THAT night. Nevermind that school had started about two weeks prior. I told her the book was out of stock and did my usual spiel, offered to take her name and contact info so we could order a copy in for her, it'll take this long to come in, etc etc. Everything was fine until I finished entering her info into our system... then she lost it. SCREAMED at me about how terrible we are, we NEVER have the books in stock (shop a bit earlier, maybe?), she's going to make sure the school's principal is made aware of this, blah blah blah. She actually told me that she was holding ME personally responsible for the fact that she couldn't buy her kid's biology textbook, even demanded to get one of my business cards (lol, I was an hourly cashier at this point) and to know my name. This went on for at least several minutes, during which the evening "supervisor" stood by - literally a few feet from me - and helped other customers while she berated me. Did absolutely nothing to intervene. I found out the next day that she called after I left that evening to ask when I'd be in the next day. I let my main supervisor know what happened and that if she called or came in, I did not want to help her. Someone actually returned a copy of the book the next day, and my supervisor held it for her even though she was not first on the list - basically just to shut her up. She actually came in a few weeks later looking for a Spanish workbook or something, and I asked her to wait while I found someone else to help her. None of that shit again (of course she was perfectly calm this time).